JSP第一篇【JSP介绍、工作原理、生命周期、语法、指令、行为】(修订版)

淡淡的烟草味﹌ 2021-09-30 21:52 212阅读 0赞

## 前言 ##

> 只有光头才能变强。
> 
> 文本已收录至我的GitHub仓库，欢迎Star：https://github.com/ZhongFuCheng3y/3y

# 什么是JSP #

JSP全名为Java Server Pages，java服务器页面。JSP是一种基于文本的程序，**其特点就是HTML和Java代码共同存在**！

# 为什么需要JSP #

**JSP是为了简化Servlet的工作出现的替代品，Servlet输出HTML非常困难，JSP就是替代Servlet输出HTML的。**

# 简单使用一下JSP #

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>简单使用JSP</title></head><body></body></html>
 <html>
 <head>
     <title>简单使用JSP</title>
 </head>
 <body>
 
 </body>
 </html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>简单使用JSP</title></head><body><%    String s = "HelloWorld";    out.println(s);%></body></html>
 <html>
 <head>
     <title>简单使用JSP</title>
 </head>
 <body>
 <%     String s = "HelloWorld";     out.println(s); %>
 </body>
 </html>

![640?wx\_fmt=png][640_wx_fmt_png]

# JSP的工作原理 #

package org.apache.jsp;import javax.servlet.*;import javax.servlet.http.*;import javax.servlet.jsp.*;import java.util.Date;public final class _1_jsp extends org.apache.jasper.runtime.HttpJspBase    implements org.apache.jasper.runtime.JspSourceDependent {  private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();  private static java.util.List<String> _jspx_dependants;  private javax.el.ExpressionFactory _el_expressionfactory;  private org.apache.tomcat.InstanceManager _jsp_instancemanager;  public java.util.List<String> getDependants() {    return _jspx_dependants;  }  public void _jspInit() {    _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();    _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());  }  public void _jspDestroy() {  }  public void _jspService(final HttpServletRequest request, final HttpServletResponse response)        throws java.io.IOException, ServletException {    final PageContext pageContext;    HttpSession session = null;    final ServletContext application;    final ServletConfig config;    JspWriter out = null;    final Object page = this;    JspWriter _jspx_out = null;    PageContext _jspx_page_context = null;    try {      response.setContentType("text/html;charset=UTF-8");      pageContext = _jspxFactory.getPageContext(this, request, response,                  null, true, 8192, true);      _jspx_page_context = pageContext;      application = pageContext.getServletContext();      config = pageContext.getServletConfig();      session = pageContext.getSession();      out = pageContext.getOut();      _jspx_out = out;      out.write("\r\n");      out.write("\r\n");      out.write("<html>\r\n");      out.write("<head>\r\n");      out.write("    <title>简单使用JSP</title>\r\n");      out.write("</head>\r\n");      out.write("<body>\r\n");    String s = "HelloWorda";    out.println(s);      out.write("\r\n");      out.write("</body>\r\n");      out.write("</html>\r\n");    } catch (Throwable t) {      if (!(t instanceof SkipPageException)){        out = _jspx_out;        if (out != null && out.getBufferSize() != 0)          try { out.clearBuffer(); } catch (java.io.IOException e) {}        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);      }    } finally {      _jspxFactory.releasePageContext(_jspx_page_context);    }  }}
 
 import javax.servlet.*;
 import javax.servlet.http.*;
 import javax.servlet.jsp.*;
 import java.util.Date;
 
 public final class _1_jsp extends org.apache.jasper.runtime.HttpJspBase     implements org.apache.jasper.runtime.JspSourceDependent {
 
 
   private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();
 
   private static java.util.List<String> _jspx_dependants;
 
   private javax.el.ExpressionFactory _el_expressionfactory;
   private org.apache.tomcat.InstanceManager _jsp_instancemanager;
 
   public java.util.List<String> getDependants() {
 
     return _jspx_dependants;
   }
 
   public void _jspInit() {
 
     _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
     _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
   }
 
   public void _jspDestroy() {
 
   }
 
   public void _jspService(final HttpServletRequest request, final HttpServletResponse response)         throws java.io.IOException, ServletException {
 
 
     final PageContext pageContext;
     HttpSession session = null;
     final ServletContext application;
     final ServletConfig config;
     JspWriter out = null;
     final Object page = this;
     JspWriter _jspx_out = null;
     PageContext _jspx_page_context = null;
 
 
     try {
 
       response.setContentType("text/html;charset=UTF-8");
       pageContext = _jspxFactory.getPageContext(this, request, response,
                   null, true, 8192, true);
       _jspx_page_context = pageContext;
       application = pageContext.getServletContext();
       config = pageContext.getServletConfig();
       session = pageContext.getSession();
       out = pageContext.getOut();
       _jspx_out = out;
 
       out.write("\r\n");
       out.write("\r\n");
       out.write("<html>\r\n");
       out.write("<head>\r\n");
       out.write("    <title>简单使用JSP</title>\r\n");
       out.write("</head>\r\n");
       out.write("<body>\r\n");
 
     String s = "HelloWorda";
     out.println(s);
 
       out.write("\r\n");
       out.write("</body>\r\n");
       out.write("</html>\r\n");
     } catch (Throwable t) {
 
       if (!(t instanceof SkipPageException)){
 
         out = _jspx_out;
         if (out != null && out.getBufferSize() != 0)
           try { out.clearBuffer(); } catch (java.io.IOException e) {}
         if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
       }
     } finally {
 
       _jspxFactory.releasePageContext(_jspx_page_context);
     }
   }
 }

out.write("\r\n");out.write("\r\n");out.write("<html>\r\n");out.write("<head>\r\n");out.write("    <title>简单使用JSP</title>\r\n");out.write("</head>\r\n");out.write("<body>\r\n");
 out.write("\r\n");
 out.write("<html>\r\n");
 out.write("<head>\r\n");
 out.write("    <title>简单使用JSP</title>\r\n");
 out.write("</head>\r\n");
 out.write("<body>\r\n");

String s = "HelloWorda";out.println(s);
    out.println(s);

--------------------

# JSP生命周期 #

JSP也是Servlet，运行时只有一个实例，**JSP初始化和销毁时也会调用Servlet的init()和destroy()方法**。另外，JSP还有自己初始化和销毁的方法

public void _jspInit() {_el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();_jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());}public void _jspDestroy() {}
    _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
    _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
    }
    
    public void _jspDestroy() {
        
    }

# JSP的语法 #

JSP代码可以分为两部分：

1.  **模板数据：就是HTML代码**
2.  **元素：JSP页面中的java代码、JSP指令、JSP标签**

## JSP脚本 ##

<jsp:scriptlet>    String s = "HelloWorld";    out.println(s);</jsp:scriptlet>
     String s = "HelloWorld";
     out.println(s);
 
 </jsp:scriptlet>

## JSP注释 ##

<%--这是JSP注释--%><%--%>//这是java的当行注释///*这是java的多行注释*//**/
 
 //这是java的当行注释
 //
 
 
 /*这是java的多行注释*/
 /**/

--------------------

## JSP指令 ##

**JSP指令用来声明JSP页面的相关属性，例如编码方式、文档类型等等**

JSP指令的语法：

<%@指令  属性名="值"  %>

### page指令 ###

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

![640?wx\_fmt=png][640_wx_fmt_png 1]

<%@ page contentType="application/msword;charset=UTF-8" language="java" %><html><head>    <title>简单使用JSP</title></head><body>    1111</body></html>"java" %>
 <html>
 <head>
     <title>简单使用JSP</title>
 </head>
 <body>
 
     1111
 </body>
 </html>

--------------------

<%@ page contentType="text/html;charset=UTF-8" language="java" errorPage="error.jsp" %><html><head>    <title>该页面出错了！</title></head><body>    <%--模拟页面出错了！！！--%>    <%        int result = 2 / 0;    %>    你好呀</body></html>"java" errorPage="error.jsp" %>
 <html>
 <head>
     <title>该页面出错了！</title>
 </head>
 <body>
     <%--模拟页面出错了！！！--%>
     <%
         int result = 2 / 0;
     %>
     你好呀
 </body>
 </html>

<%@ page contentType="text/html;charset=UTF-8" language="java" isErrorPage="true"   %><html>    <head>        <title>友好提示页面</title>    </head>    <body>        服务器正忙着呢！    </body></html>"java" isErrorPage="true"   %>
 <html>
     <head>
         <title>友好提示页面</title>
     </head>
     <body>
         服务器正忙着呢！
     </body>
 </html>

![640?wx\_fmt=gif][640_wx_fmt_gif]

<error-page>    <error-code>404</error-code>    <location>/error.jsp</location></error-page><error-page>    <exception-type>java.lang.NullPointerException</exception-type>    <location>/error.jsp</location></error-page>
     <error-code>404</error-code>
     <location>/error.jsp</location>
 </error-page>
 
 <error-page>
     <exception-type>java.lang.NullPointerException</exception-type>
     <location>/error.jsp</location>
 </error-page>

![640?wx\_fmt=gif][640_wx_fmt_gif 1]

--------------------

### include指令 ###

<%@ page contentType="text/html;charset=UTF-8" language="java"   %><html>    <head>        <title>页头</title>    </head>    <body>    我是页头                   </body></html>"java"   %>
 <html>
     <head>
         <title>页头</title>
     </head>
     <body>
     我是页头
      
      
      
     </body>
 </html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>页尾</title></head><body>我是页尾</body></html>"java" %>
 <html>
 <head>
     <title>页尾</title>
 </head>
 <body>
 
 我是页尾
 
 </body>
 </html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>包含页头和页尾进来</title></head><body><%@include file="head.jsp" %><%@include file="foot.jsp" %></body></html>"java" %>
 <html>
 <head>
     <title>包含页头和页尾进来</title>
 </head>
 <body>
 
 
 <%@include file="head.jsp" %>
 <%@include file="foot.jsp" %>
 </body>
 </html>

![640?wx\_fmt=png][640_wx_fmt_png 2]![640?wx\_fmt=png][640_wx_fmt_png 3]

--------------------

### taglib指令 ###

--------------------

## JSP行为 ##

> **JSP行为（JSP Actions）是一组JSP内置的标签**，只书写少量的标记代码就能够使用JSP提供丰富的功能，**JSP行为是对常用的JSP功能的抽象和封装**。

为什么我不把它直接称为JSP标签呢？**我把这些JSP内置的标签称之为JSP行为，能够和JSTL标签区分开来**。当然了，你也可以把它称之为JSP标签，你不要搞混就行了。我个人喜欢把这些JSP内置标签称之为JSP行为。

### include行为 ###

<jsp:include page=""/>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>包含页头和页尾进来</title></head><body>    <jsp:include page="head.jsp"/>    <jsp:include page="foot.jsp"/></body></html>"java" %>
 <html>
 <head>
     <title>包含页头和页尾进来</title>
 </head>
 <body>
     <jsp:include page="head.jsp"/>
     <jsp:include page="foot.jsp"/>
 </body>
 </html>

![640?wx\_fmt=png][640_wx_fmt_png 4]![640?wx\_fmt=png][640_wx_fmt_png 5]

<%@ page contentType="text/html;charset=UTF-8" language="java"   %><html>    <head>        <title>页头</title>    </head>    <body>    <%        String s = "zhongfucheng";    %>    我是页头呀                   </body></html>"java"   %>
 <html>
     <head>
         <title>页头</title>
     </head>
     <body>
 
     <%
         String s = "zhongfucheng";
     %>
     我是页头呀
      
      
      
     </body>
 </html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>页尾</title></head><body><%    String s = "zhongfucheng";%>我是页尾呀</body></html>"java" %>
 <html>
 <head>
     <title>页尾</title>
 </head>
 <body>
 <%
     String s = "zhongfucheng";
 %>
 
 我是页尾呀
 
 </body>
 </html>

![640?wx\_fmt=png][640_wx_fmt_png 6]![640?wx\_fmt=png][640_wx_fmt_png 7]![640?wx\_fmt=png][640_wx_fmt_png 8]![640?wx\_fmt=png][640_wx_fmt_png 9]

--------------------

### param行为 ###

### forward行为 ###

<jsp:forward page=""/>

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>    <title>访问1.jsp就跳转到head.jsp</title></head><body><jsp:forward page="head.jsp"/></body></html>"java" %>
 <html>
 <head>
     <title>访问1.jsp就跳转到head.jsp</title>
 </head>
 <body>
 
 <jsp:forward page="head.jsp"/>
 
 
 </body>
 </html>

![640?wx\_fmt=png][640_wx_fmt_png 10]

<jsp:forward page="head.jsp">    <jsp:param name="username" value="zhongfucheng"/></jsp:forward>
     <jsp:param name="username" value="zhongfucheng"/>
 </jsp:forward>

<%    String ss = request.getParameter("username");%>获取到的参数是：<%=ss%>"username");
 %>
 
 获取到的参数是：
 <%=ss%>

![640?wx\_fmt=png][640_wx_fmt_png 11]

### directive行为 ###

<jsp:directive.include file="head.jsp"></jsp:directive.include><jsp:directive.include file="foot.jsp"></jsp:directive.include>
 <jsp:directive.include file="foot.jsp"></jsp:directive.include>

![640?wx\_fmt=png][640_wx_fmt_png 12]

### javaBean行为 ###

<jsp:useBean id=""/><jsp:setProperty name="" property=""/><jsp:getProperty name="" property=""/>
 
 <jsp:setProperty name="" property=""/>
 
 <jsp:getProperty name="" property=""/>

## 最后 ##

##  ##

> 乐于输出**干货**的Java技术公众号：Java3y。公众号内有200多篇**原创**技术文章、海量视频资源、精美脑图，不妨来**关注**一下！

![640?wx\_fmt=jpeg][640_wx_fmt_jpeg]

有帮助？好看！转发！ ![640][]

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